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Abstract:

A bumper system includes a bumper beam having top and bottom attachment
features, such as apertures or concavities for attachment. A thermoformed
polymeric energy absorber includes a base flange for engaging the face of
the beam, protruding crush lobes for absorbing energy upon an impact, and
top and bottom rear flanges. The top and bottom rear flanges include
inwardly-facing protrusions defining a second dimension less than a first
dimension of the beam's face, but the base flange is sufficiently
resilient and flexible at desired locations and with desired force of
flexures to provide tunable flexure points so the protrusions can be
temporarily resiliently flexed apart to the first dimension for assembly
and then upon release, the protrusions flex back to the second dimension
engaging the attachment features to temporarily but positively retain the
energy absorber on the beam.

Claims:

1. A bumper system for a passenger vehicle comprising: a bumper beam
having face, top and bottom surfaces, with the top and bottom surfaces
including attachment features that are one of apertures or concavities
for attachment; the top and bottom surfaces defining a first vertical
dimension; and an energy absorber with a base flange for engaging the
face surface, protruding crush lobes for absorbing energy upon an impact,
and top and bottom rear flanges; the top and bottom rear flanges
including inwardly-facing protrusions defining a second dimension less
than the first dimension but the base flange being sufficiently resilient
and flexible to provide tunable flexure points where the protrusions can
be temporarily flexed apart to the first dimension for assembly and then
upon release the protrusions flex back to the second dimension engaging
the one attachment feature to temporarily retain the energy absorber on
the beam.

2. The bumper system defined in claim 1, wherein the one includes the
apertures.

3. The bumper system defined in claim 1, wherein the one includes the
concavities.

4. The bumper system defined in claim 1, wherein the one includes at
least one longitudinally-extending concave channel.

5. The bumper system defined in claim 1, wherein the protrusions include
at least one longitudinally-extending ridge.

6. The bumper system defined in claim 1, wherein the protrusions form
opposing jaws that self-clamp onto the beam.

7. The bumper system defined in claim 1, wherein the protrusions form a
plurality of opposing jaw pairs spaced longitudinally apart.

8. The bumper system defined in claim 1, wherein energy absorber
comprises a thermoformed polymeric sheet that is heated and formed into a
three-dimensional component.

9. A method of assembly comprising steps of: providing a bumper beam
having face, top and bottom surfaces, with the top and bottom surfaces
including attachment features that are one of apertures or concavities
for attachment; the top and bottom surfaces defining a first vertical
dimension; providing an energy absorber with a base flange for engaging
the face surface, protruding crush lobes for absorbing energy upon an
impact, and top and bottom rear flanges; the top and bottom rear flanges
including inwardly-facing protrusions defining a second dimension less
than the first dimension; and assembling the energy absorber onto the
beam by resiliently flexing the base flange where the protrusions are
temporarily flexed apart to the first dimension for assembly and then
upon release the protrusions flex back to the second dimension to
temporarily engage the one attachment feature to retain the energy
absorber on the beam.

10. A method of thermoforming an energy absorber component comprising
steps of: providing tooling having a molding surface shaped to form an
energy absorber with a base flange and protruding crush lobes for
absorbing energy upon an impact, and top and bottom rear flanges; heating
a polymeric sheet of material and forming same on the tooling including
forming a base flange having a first dimension and forming top and bottom
rear flanges with inwardly-facing protrusions defining a second dimension
less than the first dimension; and removing the energy absorber from the
tooling by resiliently flexing the base flange where the protrusions are
temporarily flexed apart to the first dimension and then upon release,
allowing the protrusions to flex back to the second dimension.

11. The method defined in claim 10, including a step of attaching the
energy absorber to a bumper beam by resiliently flexing the protrusions
apart for assembly and then releasing the energy absorber so that the
protrusions flex back and into engagement with the beam.

12. The method defined in claim 10, including a step of attaching the
energy absorber to a beam by resiliently flexing the protrusions apart
for assembly and then releasing the energy absorber so that the
protrusions flex back and into engagement with the beam, thus acting as a
spacer on the beam.

13. A bumper system for a passenger vehicle comprising: a bumper beam
having front, top, bottom and rear surfaces; the top and bottom surfaces
defining a first vertical dimension; and an energy absorber with a base
flange for engaging the front surface, protruding crush lobes for
absorbing energy upon an impact, and top and bottom rear flanges; the top
and bottom rear flanges including inwardly-facing protrusions defining a
second dimension less than the first dimension but the base flange being
sufficiently resilient and flexible so the protrusions can be temporarily
flexed apart to the first dimension for assembly and then upon release
the protrusions flex back to the second dimension engaging a rear surface
of the beam to retain the energy absorber on the beam.

14. A system comprising: a beam having front, rear, top and bottom
surfaces; the top and bottom surfaces defining a first vertical
dimension; and a thermoformed energy absorber with a base flange for
engaging the front surface, protruding crush lobes for absorbing energy
upon an impact, and top and bottom rear flanges; the top and bottom rear
flanges including inwardly-facing protrusions defining a second dimension
less than the first dimension but the base flange being sufficiently
resilient and flexible the protrusions can be temporarily flexed apart to
the first dimension for assembly onto the beam and then upon release the
protrusions flex back to the second dimension engaging the beam to
temporarily retain the energy absorber on the beam as a front spacer on
the beam.

[0002] The present invention relates to bumper systems for passenger
vehicles, and more particularly to a bumper system having a beam and
thermoformed energy absorber that resiliently friction-fits onto the beam
with sufficient force for self-retention. However, it is contemplated
that the present invention is not limited to only thermoforming processes
nor thermoformed parts, nor to bumper beams, nor to passenger vehicles.

BACKGROUND

[0003] Passenger vehicles require bumper systems to protect vehicle
components, reduce injury to pedestrians, and translate load for the
triggering of air bag deployment during an impact. Often, a polymeric
energy absorber is fastened to a bumper system by press-fit or secondary
fasteners (e.g., screws, push pins, or brackets) and/or is attached via
secondary processes (e.g., welding, bending, or bonding), or is held in
place by other means (e.g., by attaching the energy absorber to a RIM
fascia cover aesthetically covering a front end of a vehicle). However,
secondary fasteners and processes add expense due to the use of
additional parts, additional manpower, and additional assembly time.

[0004] Injection molded energy absorbers sometimes have attachment flanges
with integral connectors. However, integral connectors add cost to the
tooling, particularly where they require slides or cams for action in the
mold tooling . . . , which is usually the case for positively-engaging
integral connectors, since these connectors require blind surfaces for
creating the positive retention. Persons skilled in the art of injection
molding understand that it is difficult to release molded parts with
blind surfaces from mold tooling unless there are slides or cams in the
tooling to eliminate interference conditions that prevent release of the
parts. However, slide and/or cams add considerable expense to injection
molding tooling and to maintenance costs. Persons skilled in the
automotive industry know that it is extremely competitive, and that every
additional fastener or additional secondary attachment process costs
money, time, and effort. Also, complex and expensive tools add to
overhead costs

SUMMARY

[0005] In one aspect of the present invention; a bumper system for a
passenger vehicle including a bumper beam having face, top and bottom
surfaces, with the top and bottom surfaces including attachment features
that are one of apertures or concavities for attachment; the top and
bottom surfaces defining a first vertical dimension. The bumper system
further includes an energy absorber with a base flange for engaging the
face surface, protruding crush lobes for absorbing energy upon an impact,
and top and bottom rear flanges. The top and bottom rear flanges include
inwardly-facing protrusions defining a second dimension less than the
first dimension but the base flange is sufficiently resilient at tunable
flexure points where the protrusions can be temporarily flexed apart to
the first dimension for assembly and then upon release the protrusions
flex back to the second dimension engaging the one attachment feature to
temporarily retain the energy absorber on the beam.

[0006] In another aspect of the present invention, a method of assembly
comprises steps of providing a bumper beam having face, top and bottom
surfaces, with the top and bottom surfaces including attachment features
that are one of apertures or concavities for attachment; the top and
bottom surfaces defining a first vertical dimension; providing an energy
absorber with a base flange for engaging the face surface, protruding
crush lobes for absorbing energy upon an impact, and top and bottom rear
flanges; the top and bottom rear flanges including inwardly-facing
protrusions defining a second dimension less than the first dimension;
and assembling the energy absorber onto the beam by resiliently flexing
the base flange where the protrusions are temporarily flexed apart to the
first dimension for assembly and then upon release the protrusions flex
back to the second dimension to temporarily engage the one attachment
feature to retain the energy absorber on the beam.

[0007] In yet another aspect of the present invention, a method of
thermoforming an energy absorber for a vehicle bumper system includes
steps of providing tooling having a molding surface shaped to form an
energy absorber with a base flange and protruding crush lobes for
absorbing energy upon an impact, and top and bottom rear flanges; heating
a polymeric sheet of material and forming same on the tooling including
forming a base flange having a first dimension and forming top and bottom
rear flanges with inwardly-facing protrusions defining a second dimension
less than the first dimension; and removing the energy absorber from the
tooling by resiliently flexing the base flange where the protrusions are
temporarily flexed apart to the first dimension and then upon release,
allowing the protrusions to flex back to the second dimension.

[0008] In one aspect of the present invention, a bumper system for a
passenger vehicle comprises a bumper beam having front, top, bottom and
rear surfaces; the top and bottom surfaces defining a first vertical
dimension; and an energy absorber with a base flange for engaging the
front surface, protruding crush lobes for absorbing energy upon an
impact, and top and bottom rear flanges. The top and bottom rear flanges
include inwardly-facing protrusions defining a second dimension less than
the first dimension but the base flange is sufficiently resilient and
flexible so the protrusions can be temporarily flexed apart to the first
dimension for assembly and then upon release the protrusions flex back to
the second dimension engaging a rear surface of the beam to retain the
energy absorber on the beam.

[0009] In another aspect of the present invention, a system includes a
beam having front, rear, top and bottom surfaces; the top and bottom
surfaces defining a first vertical dimension; and a thermoformed energy
absorber with a base flange for engaging the front surface, protruding
crush lobes for absorbing energy upon an impact, and top and bottom rear
flanges. The top and bottom rear flanges include inwardly-facing
protrusions defining a second dimension less than the first dimension but
the base flange is sufficiently resilient and flexible the protrusions
can be temporarily flexed apart to the first dimension for assembly onto
the beam and then upon release the protrusions flex back to the second
dimension engaging the beam to temporarily retain the energy absorber on
the beam as a front spacer on the beam.

[0010] These and other aspects, objects, and features of the present
invention will be understood and appreciated by those skilled in the art
upon studying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a vertical cross-sectional view of a bumper system
including a bumper beam and self-attached energy absorber.

[0012] FIG. 2 is a perspective view of the energy absorber of FIG. 1.

[0013] FIG. 3 is an enlarged view of the flexing engagement of the energy
absorber with the beam from FIG. 1.

[0014] FIGS. 4-5 are vertical cross-sectional and perspective views of a
modified beam and energy absorber, the views FIGS. 4-5 being similar to
FIGS. 1-2.

DETAILED DESCRIPTION

[0015] As required, detailed embodiments of the present invention are
disclosed herein; however, it is to be understood that the disclosed
embodiments are merely exemplary of the invention that may be embodied in
various and alternative forms. The figures are not necessarily to scale;
some features may be exaggerated or minimized to show details of
particular components. Therefore, specific structural and functional
details disclosed herein are not to be interpreted as limiting, but
merely as a representative basis for teaching one skilled in the art to
variously employ the present invention.

[0016] A vehicle bumper system 20 (FIGS. 1-3) includes a bumper beam 21
and a thermoformed energy absorber 22 that "snaps" onto a face of the
beam 21 for self-retention. The illustrated beam 21 is a single-tube beam
that includes integrally-formed top and bottom attachment features, such
as apertures 23 (or flanges or channels or concavities, not specifically
shown) for frictionally positive engagement with a mating feature (i.e.,
protrusions 29/30) on the energy absorber 22.

[0017] The thermoformed polymeric energy absorber 22 includes a base
flange 24 for engaging the face 25 (e.g., front wall) of the beam 21,
protruding crush lobes 26 (two rows shown, most being cone shaped, but
more or less a different arrangement of crush lobes or modified crush
lobes could be used, such as a modified smaller crush lobe at each end)
for absorbing energy upon an impact, and top and bottom rear flanges 27
and 28. The top and bottom rear flanges 27 and 28 include inwardly-facing
undercuts or protrusions 29 and 30 defining a second dimension D2 less
than a first dimension D1 of the beam's face 25. The base flange 24
(particularly in the location 31 between the crush lobes 26) is
sufficiently resilient and flexible to provide tunable flexure points
where the protrusions 29 and 30 can be temporarily resiliently flexed
apart (noting that the gradient of the flexure can be tuned from 29 to
30, such that one is more rigid than the other) to the first dimension Dl
for assembly and then upon release, the protrusions 29 and 30 flex back
to the second dimension D2 engaging the attachment features (apertures
23) to temporarily but positively retain the energy absorber 22 on the
beam 21 until the fascia is attached over the bumper system 20. Notably,
a resiliency of the location 31 can be tuned for optimal
gripping/clamping action (and insertion/retention),--such as by adding
channel ribs (shown) or changing a material thickness or embossment at
that location. It is contemplated that the protrusions 29-30 could be
made to engage a rear surface of the beam 21 instead of the features 23.

[0018] It is noted that a cross car locator can be formed in the energy
absorber 22, such as by forming a lobe extending into a hole in the
bumper beam's front wall. It is also contemplated that the energy
absorber 22 could be formed with ends that resiliently flex and engage
ends of the beam 21.

[0019] It has been found that the attachment scheme for the energy
absorber 22 can be improved to meet customer expectations so that the
energy absorber remains on the beam after sequential FMVSS tests. The
improvement is made by adding the spaces 37 in energy absorber 22 (FIG.
2) at center and end locations near attachments/snaps. The spaces 37 are
created by basically eliminating columns of cones nearest to snaps, which
prevents the energy absorber 22 from splaying open during impact and
releasing from the associated beam. Specifically, testing has shown that
a footprint of an energy absorber 22 may increase as its lobes 26 become
compressed and individual lob base diameters increase (i.e. open up). The
increase in footprint could cause an energy absorber to disengage from
the beam 21 prior to the final impact in a series of impacts/collisions.
Straps/spaces 37 are areas of the energy absorber that are void of lobes.
Straps/spaces 37 can be added between protrusions 29/30 to prevent the
distance between such protrusions from increasing during impact.

[0020] Modified bumper systems are shown in FIGS. 3 and 4-5. In these
systems, similar and identical components and features are identified
using the same numbers, but with the addition of a letter "A" or "B".

[0021] In FIG. 3, the protrusion 29A engages a concavity 23A in a modified
beam 21A. The illustrated beam 21A includes a longitudinally extending
down (or up) flange 33A forming with a remainder of the beam 21A the
concavity 23A. Notably, the channel can be either spaced apart short
depressions along a length of the beam, or a continuous long channel
along the beam 21A. The illustrated beam 21A is an aluminum extrusion
with a down flange 33A forming the recess 23A. However, it is
contemplated that the beam 21A could be roll formed to include a channel
recess or a doubled-back wall section forming the recess 23A adjacent a
back side of the flange 33A. The beam can also be stamped, hot-stamped
LFT, composite, or other. The illustrated flanges 27A (and protrusions
29A) extend in an undercut direction D3 by at least about 4-5 mm (and
more preferably about 4 mm) and has a first wall 35A at an angle A1 of
about 15 to 60 degrees or more preferably about 30 to 45 degrees for
providing positive retention after engagement, and has a second trailing
wall 36A at an angle A2 of about 5 to 45 degrees or more preferably about
10 to 30 degrees for providing an easier insertion force for assembly of
the energy absorber 22A onto the beam 21A (i.e., insertion/retention
forces can be tuned to meet customer requirements). Also, the length of
the trailing wall 36A can be made longer than the first wall 35A, if
desired in order to provide a longer ramp to facilitate assembly.

[0022] The bumper system 20B (FIGS. 4-5) includes a double-tube beam 21B
and energy absorber 22B. The features are generally similar and the
discussion of same will not be repeated. It is noted that the crush lobes
26B at each end are modified to be T-shaped. The protrusions 29B and 30B
are slightly deeper and the wall thickness increased in energy absorber
22B, such that it is noted that the thermoform tooling may require action
(i.e., a cam or slide) in order to easily release the energy absorber 22B
from the thermoform tooling die.

[0023] There are several advantages to the present inventive concepts.
This is the first time that flanges on a beam have been used to attach a
thermoformed energy absorber to a bumper beam. The attachment system is
relatively simple and the parts are relatively easy make (i.e., roll form
or extrude or other manufacturing methods of the beam 21, 21A, 22A, or
thermoform the energy absorber 22, 22A, 22B). Notably the attachment
system can be tuned to provide an optimal force of assembly and optimal
retention force to prevent disassembly. For example, a bending resiliency
of the base flange (especially the area 31 between the top and bottom
crush lobes 26) can be affected by the material properties, increasing or
decreasing wall thickness, addition of channel ribs or ridges for
selective stiffening, and other means. Notably, the undercuts or
protrusions 29 and 30 are small enough to be released from the thermoform
tool without requiring action in the mold tooling. (It is noted that the
thermoform tooling could include slides or cams in order to produce the
undercuts, however, it is not contemplated that this would be required
since the thermoformed energy absorbers can be flexed to release the
protrusions 29 and 30 from the tooling without substantial difficulty.
Nonetheless, a slide/cam may be used in the thermoform tooling if the
undercuts are more than 5 mm deep.)

[0024] The resiliency of the energy absorber 22 causes the energy absorber
22 to engage the beam 21 in a manner that reduces or eliminates buzzes,
squeaks and/or rattles, which can be a problem in vehicles at certain
vibrations. The retention strength is easily adjusted, such as by
changing an insertion or retention angle of the mating surfaces of the
protrusions 29/30 and the attachment features (i.e., apertures 23 or
mating channels), or by providing slits or breeches or gusset ribs in the
energy absorber 22. Further, the aperture 23 in the beam 21 can include a
relatively sharp corner that engages the protrusions 29/30, making the
beam 21 bite into the energy absorber for increased retention force.

[0025] The present system has several advantages, including elimination of
secondary fasteners, reduced steps in the manufacture of parts and in the
assembly of parts, reduced risk of buzzes/squeaks/rattles, reduced need
for secondary equipment at the assembly plant and concurrent savings in
floor space, reduced overall mass due to use of a thermoformed sheet
product rather than an injection molded energy absorber, and reduces
overall system cost versus other systems (such as systems using separate
fasteners and/or EPP foam).

[0026] It is noted that the energy absorber 22 is thermoformed from a
sheet of polymer having a uniform thickness. The sheet is heated and then
drawn down onto a thermoform mold into the shape of the final energy
absorber. It is contemplated that different thermoform processes can be
used to manufacture the energy absorber 22, such as vacuum thermoforming,
and that the thermoforming process can use a single lower die or pair of
top and bottom opposing dies.

[0027] While exemplary embodiments are described above, it is not intended
that these embodiments describe all possible forms of the invention.
Rather, the words used in the specification are words of description
rather than limitation, and it is understood that various changes may be
made without departing from the spirit and scope of the invention.
Additionally, the features of various implementing embodiments may be
combined to form further embodiments of the invention.